Darth is right about kois being marbles(as expressed by you admittingra his color has changed slightly since getting him).
But breeding marble to marble doesn't make it skip a generation.
Breeding koi to koi you won't necessarily get koi. This is because the marble gene is, for the most part, unpredictable. getting a 'fancy' marble is up to luck in part with the genetics.
You'll get a mix of solids,multies,marbles,butterflies...it's a grab bag really.
If one is orange or yellow as opposed to red, I'd try to find a match for that(another orange for an orange or yellow for a yellow) otherwise your fry will show red(unless it carries the other color). But this is just me since I try to avoid red as a personal preference.

here are a couple articles you may find interesting for breeding marbles.:some info #1

Getting them to spawn is my main task at the moment. Been trying for over a month now and still nothing. Just set up the spawn tank last night for my 3rd or 4th attempt. The female is always excited to see the male when in a separate tank but once together she seems intimidated by him so what I'm trying differently this time is to provide a better hideout so she can hide until she feels comfortable to come out.

Which is fine curly-fat-bottom, but however I have bred marble x marble and gotten marble. I think the point of this small little spat is that we don't necessarily want to steer ppl in a direction that can't be backed by fact. & for somebody to say they have bred for X amount of time is not a qualification/credential when somebody who has bred 6 months bred marble x marble and got more marble....confused... i mean isn't marrble the jumping gene. it can choose to express itself WHENEVER it wants...